1. Field of the Invention
The present invention relates to a printhead element substrate having a connection status output circuit which outputs a signal reflecting the electrical connection status between a printhead and a printing apparatus, a printhead, a head cartridge, and a printing apparatus.
2. Description of the Related Art
An inkjet printing apparatus is a so-called non-impact printer and is capable of executing high-speed printing, printing on various kinds of print media, and almost noise-free printing. For these reasons, the inkjet printing apparatus is widely employed as an apparatus serving as the printing mechanism of a printer, copying machine, facsimile apparatus, or wordprocessor.
Well-known typical ink discharge methods adopted by a printhead in an inkjet printing apparatus are, e.g., a method using an electromechanical transducer such as a piezoelectric element, and a method using an electrothermal transducer (heater) which heats ink to discharge ink droplets by a film boiling effect.
A printing apparatus having such an inkjet printhead can output high-resolution characters and images at a low cost. Especially, the printer which discharges ink droplets by the film boiling effect commands a large share of the market because it can perform color printing at a low cost.
The number of orifices of a printhead increases from 64 to 128 or 256 with a tendency toward a higher image quality. The number of orifices per inch (dpi) increases to 300 dpi or 600 dpi, and the orifices are arranged at a high density. A heater serving as an electrothermal transducer arranged in correspondence with each orifice forms bubbles by film boiling upon receiving a heat pulse in the order of several to 10 μsec. Such high-frequency driving implements high-speed high-quality printing.
A unit for electrically connecting the printhead in the inkjet printing apparatus is provided on the carriage which reciprocally moves the attached printhead. More specifically, the carriage has a plurality of contacts. When the printhead is attached to the carriage, these contacts come into contact with a plurality of contacts provided on the printhead side. This ensures electrical connection between the printhead and the inkjet printing apparatus.
U.S. Pat. No. 5,828,386 discloses a printhead having a unit for monitoring the electrical connection status. More specifically, the printhead comprises an AND circuit which calculates the logical product of print data input from a printing apparatus to the printhead, a clock signal to transfer the print data, and a logical signal to make the apparatus execute a printing operation corresponding to the print data, and an output terminal which outputs the calculation result. This arrangement prevents any print failure such as lack of printing dots or printhead malfunction caused by a contact failure. Such a unit for confirming the connection status is particularly important in an ink-tank-integrated printhead detachable from the main body of an inkjet printing apparatus.
In this prior art, after confirming that the contact statuses of terminals for receiving logical signals (e.g., print data, clock signal, and control signal) are normal, a high voltage of, e.g., 24 V is applied to the printhead. If the terminals short-circuit, or a wiring portion that receives the high voltage has a connection error, the printhead may malfunction even when the contact statuses of the terminals appear to be normal.